The feature matching takes the reference data and attempts to identify corresponding features in the OSM data set. Feature matching is a necessary precondition to compare single features rather than feature characteristics on study area a grid cell level.
Method
Matching features in two road data sets with each their way of digitizing features and a potential one-to-many relationship between edges (for example in the case where one data set only maps road center lines, while the other map the geometries of each bike lane) is not a trivial task.
The method used here converts all network edges to smaller segments of a uniform length before looking for a potential match between the reference and the OSM data. The matching is done on the basis of the buffered distance between objects, the angle, and the undirected Hausdorff distance, and is based on the works of Koukoletsos et al. (2012) and Will (2014).
Based on the matching results, the following values are computed:
Interpretation
It is important to visually explore the feature matching results, since the success rate of the matching influences how the analysis of number of matches should be interpreted.
If the features in the two data sets have been digitized differently - e.g. if one data set has digitized bike tracks as mostly straight lines, while the other includes more winding tracks, the matching will fail. This is also the case if they are placed too far from each other. If it can be confirmed visually that the same features do exist in both data sets, a lack of matches indicates that the geometries in the two data sets are too different. If however it can be confirmed that most real corresponding features have been identified, a lack of matches in an area indicates errors of commission or omission.
Segments created successfully! Starting matching process using a buffer distance of 15 meters, a Hausdorff distance of 17 meters, and a max angle of 30 degrees. Buffer matches found! Continuing with final matching process... 60809 reference segments were matched to OSM edges 2886 reference segments were not matched Feature matching completed!